Warning sign



FIG. 1 is a front elevational view of a warning sign showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a perspective view.

The broken line showing is included for the purpose of illustrating portions of the “article” and forms no part of the claimed design. 

CLAIM The ornamental design for a warning sign, as shown and described. 